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Thread: Electrical brake for AC motors

  1. #1
    Supporting Member 2gsg2_muc's Avatar
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    Electrical brake for AC motors

    When thread cutting on the lathe, it is easier if the motor can be braked automatically. This can be done simply by short-circuiting the windings by means of the counter electromotive force generated. For this purpose, the auxiliary switch of the contactor of the drive motor must have 2 free closing contacts. In the case of a single-phase motor, only one phase must be short-circuited via the make contacts of the contactors for both directions of rotation with the second phase via a 2-pole brake switch. With a 3-pole motor, the second phase must also be routed via the make contacts of the contactors, and the third phase is then connected to the short-circuited contacts of the brake switch. The wiring can be found in the wiring diagram. The required auxiliary contacts can be ordered from the contactor manufacturer. Since usually only 2-pole auxiliary switches are installed, these can simply be replaced with a 4-pole auxiliary switch with three make contacts and one break contact.




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  2. The Following 5 Users Say Thank You to 2gsg2_muc For This Useful Post:

    EnginePaul (Apr 11, 2023), Jon (Jan 26, 2023), nova_robotics (Feb 21, 2023), Scotty1 (Feb 11, 2023), uv8452 (Feb 26, 2023)

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    schematic for easier understanding

    Prinzischaltpan der Motorbremse.
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    nova_robotics (Feb 21, 2023), Scotty1 (Feb 21, 2023), uv8452 (Feb 26, 2023)

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    Thanks 2gsg2_muc! We've added your AC Motor Brake to our Electrical category,
    as well as to your builder page: 2gsg2_muc's Homemade Tools. Your receipt:




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    Video How the Circuit is working

    The first switch is for the power supply, the second for baraking function

    [video] https://www.dropbox.com/s/0lm75yl98t...hort-.mp4?dl=0
    Last edited by 2gsg2_muc; Feb 11, 2023 at 03:44 PM.

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    Hello,

    now I want to show you how I installed the Aotostop at my CJM250 using shorting of the motor when threading. I made a little box with a limit switch, which can be slided over the lathe bed to adjust the sto point. The wiring is implementet to the regular stop switch of the lathe. it contains also two LED indicating the state of the motor. Green means the motor can be startet for threading, when the slide reaches the actuator of the switch it will stop the motor imdiately. The motor can be startet only in reverse direction again, to start a new turn for threading. t works exelent at a speed between 50 and 150 RPM. Do not forget to switch to autostop funktion bevore threading.

    Electrical brake for AC motors-autostop-controlbox.jpgElectrical brake for AC motors-autostopp-clear.jpgElectrical brake for AC motors-autostop-brake.jpg

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    nova_robotics's Tools
    Excellent work. You just gave me an idea with the box with the LEDs on it. What about using a hall effect sensor instead of a mechanical switch?

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    I do not recomment a hall sensor underneaht a cutting tool, it may disturb your motor control system.

    Attached the circuit diagram of my CJM250
    Attached Files Attached Files
    Last edited by 2gsg2_muc; Feb 22, 2023 at 11:12 AM. Reason: adding scematic

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    motor brake by short

    New improved basic circuit diagram.

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    Last edited by 2gsg2_muc; Feb 26, 2023 at 03:48 PM. Reason: Wrong PDF

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    uv8452's Tools
    Right: Even I know (and own) hermetically sealed switches I'd like something-in-a-closed-box. Inductive switch or reed switch?

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    Hello uv8452
    what you need is a contactor which can handle the load of your motor. My picture shows a toggle switch, which must be installed in a box.



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